CMMG

CMMG built its name on the AR platform and then on making it shoot things it was never designed for. Their radial delayed blowback system is the interesting piece of engineering — it allows a direct-blowback pistol-calibre carbine to run far softer and cleaner than the mass-and-spring approach everyone else uses.

That system underpins the Banshee and Resolute lines in 9mm, .45 ACP, .40 and the unusual .45 Raider and 5.7x28 chamberings, and the 9mm versions take Glock magazines, which solves the usual pistol-carbine problem of feeding an orphan magazine standard. They also sell conversion kits and complete uppers, so an existing AR lower can become a pistol-calibre carbine without a second transfer.